Add FAQ item for git history and records retention

[jordangov]

This is the guidance coming out of #67 on FOIA, records retention, and git history rewrites. This language needs a little review, but I'm generally in favor of it.

@shawoods: can you review?

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A note on git features and rewriting history

The git program and hosted services such as GitHub include the ability for you to permanently delete parts of your project. They also allow you to "rewrite history" in that you may modify entries that have been previously published. Examples include:

• Deleting a branch that has not been merged into a surviving branch
• Merging a branch using the --squash feature
• Using git push with the --force feature

Code.mil is aware of records keeping laws in 18 U.S.C. 2257. We have not studied these laws nor are we aware of any case law that prescribes whether records keeping requirements pertain to portions of your git repository. Additionally, we do not know about YOUR agency's data backup systems. When you use the three deletion/rewriting abilities above the old file versions may still be persisted on your computer (see git garbage collection) and captured by these data backup systems.

In summary, git is a powerful tool so make sure you understand it before you use it. Your agency may prescribe additional guidelines or restrictions for using git. However, code.mil has no advice to offer on setting such guidelines or restrictions.

[fulldecent]

^^ I'm the author

[jordangov]

:) I did leave that out... sorry!